Blade shrouding



Patented Aug. 20, 1940 BLADE SHROUDING East Pittsburgh, Pa., a

vania corporation of Pennsyl- Application March 1l, 1939, Serial No. 261,254

2 Claims. (C1. 253-77) This invention relates to elastic fluid turbines, and has for an object the provision of improved turbine blade shrouding which is particularly useful with high-temperature and high-pressure 5 turbines. 1

Another object of the invention is the provision of turbine blades having integral spacing pieces at their free ends cooperating to form a shroud with a circumferentially extending channel formed in the outer surface thereof, and tie members in the channel and welded to the spacing pieces at zones where danger of cracking is at a minimum.

H A further object of the invention is the pro- 1' vision of blades having integral spacing pieces cooperating to form a shroud, the shroud having a circumferentially-extending channel of dovetail section in its outer surface closely receiving unstressed tie members of similar section, and

welds securing the tie members to the spacing pieces.

These and other objects are elected by the invention as will be apparent from the following description and claims taken in connection with the accompanying `drawing forming a part of this application, in which:

Fig. 1 is a side elevational view, with a portion thereof broken away along the line I-I of Fig. 2, showing a portion of a blade row embodying the invention;

Fig. 2 is a plan view of the structure shown in Fig. 1;

Figs. 3 and 4 are transverse sectional views taken along the lines IH-III and IV-IV, re-

spectively, of Fig. 2;

Fig. 5 is a plan view of a modied construction of the invention; and,

Fig. 6 is a sectional view taken along the line VI-VI of Fig. 5. l

Referring now to the drawing more in detail, there is shown at it a blade-mounting member such as a turbine rotor carrying a plurality of blades il, the blades having integral spacing pieces I2 at their outer ends which cooperate to form a shroud for the row of blades I l.

The shroud is provided with a circumferentially-extending channel i3 (Figs. 3 and 4) of dovetail cross-section in which are disposed a plurality of tie members I4 of similar section and having a metal-to-metal lit with the walls of the groove i3.

This metal-to-metal dt is important in that the tie members lll should be in unstressed condition after insertion in the groove I3, and to this end, in actual assembly, the tie members I 4 are coated with lubricant, such as castor oil, and iorced circumferentially into the groove. As an alternative method of obtainingthe desired close fit without stressing of the tie members, the latter may be contracted by cooling in a well-known 5 manner for a period immediately preceding insertion into the channel.

The tie members I4 are provided with a plurality of circumierentially-spaced openings l5 extending therethrough, the spacing of the 10 openings being such that they coincide with the centers of the spacing pieces I2. The .openings l@ are filled with weld material I'I, serving to autogenously connect the tie members to the spacing pieces.

Inasmuch as the tie members i4 lare inserted into the groove circumferentially, it is necessary v 'to provide a tie member of special design to be inserted last through the top of the groove I3.

Such a tie piece is shown at thev left in Fig. 2 20 and in Fig. 4.

As shown in these figures, a tie member I4a is split circumferentially (Fig. 4) and the two halves are inserted into the groove through the open top thereof. The tie member Ica is pro- 25 vided with openings 56a similar to the openings l5 in the -tie strips I4. After assembly in the groove I3, weld metal Ila is applied in the openings !a. and the space between the two halves of the tie strip is filled with weld material I8 to 30 provide an autogenous connection of the two halves of the tie member.

The modification shown in Figs. 5 and 6 diiers from that of the preceding figures in thatl the openings I6 adjacent the ends of the tie strips 35 are omitted and the transverse ends of the tie strips themselves are welded directly` to the spacing pieces which they overlie, as at 2Q.

While we have shown our invention in several forms, it will be obvious to those skilled in the 40 art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art 45 or as are specically set forth in the appended claims.

What we claim is:

1. In combination with a blade-mounting element, a row of blades mounted on said element, 50 a spacing piece integral with the outer end of each blade, said spacing pieces cooperating to form a shroud for the row of blades, said shroud having an outer circumferential channel of dovetail cross-section, tie members of dovetail sec- 55 tion fitting the channel, adjacent ends of adjoining tie members being aligned with the centers of spacing pieces which they overlie, said tie members being provided with spaced openings extending therethrough and aligned with the centers of the intermediate spacing pieces, and weld material in said openings and at said ends for autogenously connecting the tie members to the spacing pieces.

2. In combination with a blade-mounting ele-` ment, a row of blades mounted on said element, a spacing piece integral With the outer end of each blade, said spacing pieces cooperating to form a shroud for the row of blades, said shroud and autogenously connecting the tie member 10 to the spacing pieces.

CARL R. SODERBERG. WILLIAM I-I. LLOYD. 

